Studies of biological processes have shown that differing biological outcomes can result from signals with identical chemical composition when the compositions are presented with differencing spatial or temporal characteristics. For example, transient responses to long-lasting changes in environmental, intercellular, and intracellular conditions are observed in many systems. These transient responses can have very different time scales that range from milliseconds to several hours and can also occur across different spatial dimensions. Examples of such transient responses include the adaptation of tumbling probabilities to nutrient levels in bacterial chemotaxis, bacterial flagellar development, somitogenesis, protein expression during embryo development, JAK/STAT immune response pathways, circadian rhythms, and various feed-forward regulatory motifs. Being able to generate representative environments will provide researchers with essential degrees of freedom when studying such dynamic biological processes.
As such, improved apparatuses and methods for generating chemical gradients are highly desirable.